In further support of the principle of legal certainty, it also establishes the condition that the crime must be one defined by law as serious; it sets a time limit - no more than 48 hours may have elapsed since the crime was committed; and it requires a preliminary investigation into the matter to have been launched and the crime to be still under investigation.
Además, dando mayor firmeza al principio de seguridad jurídica, establece como requisitos para que tal detención sea legal, que el delito imputado al indiciado sea de los que la ley califica como graves. También se establece una exigencia temporal: que no haya transcurrido un plazo de 48 horas desde el momento de la comisión de los hechos delictivos.